At 8:30 p.m. on Saturday, March 26, 2011, some of Chicago's tallest skyscrapers will turn off some lights to conserve energy. Thousands of residents also participate each year.
While Earth Hour is largely symbolic, ComEd said the hour does make a difference.
"Last year during Earth Hour customers turned off their lights and we were able to save enough energy to remove more than 124,000 pounds of carbon dioxide from the atmosphere. That's the equivalent of planting 15 acres of trees," Krissy Posey, ComEd, said.